Thread: Use appropriate identities (sin, cos, tan)
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Old December 4th, 2008, 11:30 AM
nzmathman nzmathman is offline
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\sin(4a)

= 2 \sin(2a) \cos(2a)

= 2 \times 2 \sin(a) \cos(a) \times [\cos^2(a) - \sin^2(a)]

Which gives the answer required (only the double angle formula are needed for this question).
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